When connectors are to be mated to each other, it is important that one be fully inserted and locked into the other. If there is insufficient resistance to the insertion, the danger arises that the assembler will not press the two parts together with sufficient force and, as a result, incomplete assembly is achieved. On the other hand, if excessive fitting resistance is provided, the operator may get a false impression that fitting has been completed when, in fact, this is only partially so.
To overcome the foregoing problem, an inertia locking mechanism is used. This generates an initial resistance to fitting which is greater than the fitting resistance between the terminals themselves. When the initial resistance is overcome, this resistance is quickly relaxed. This provides consistency of feel so that the operator can better judge when fitting is complete. Moreover, the momentum of the connector, which results from the release of the initial resistance, aids in completing the fitting operation.
A device of the foregoing type is shown in cross section in FIG. 7. First connector 1 is provided with locking arm 2. Second connector 3 has corresponding engagement portion 4 located thereon. When first connector 1 and second connector 3 are fitted together, locking arm 2 rides up over engagement portion 4 until it is in contact with the rear face thereof, thus locking the two parts together. The fitting resistance is generated by the front of engagement portion 4 contacting the distal end of locking arm 2. When this is overridden, locking is complete.
However, since such structure requires a substantial force to complete the fitting operation, users sometimes press down on the rear of locking arm 2 to deliberately disengage it so as to facilitate joinder of the connectors. However, since this prevents locking arm 2 from contacting engagement portion 4, the fitting resistance is either absent or substantially reduced. As a result, there is no consistent feel and it is difficult for the operator to know whether the assembly is complete.
An alternative device is disclosed in Japanese Utility Model Laid-Open Publication 2-95174 and is shown in perspective in FIG. 8 hereof. There is provided a pair of spaced apart locking arms 5. Between them, resistance arm 6 is located. Locking arms 5 act in the same way as the corresponding locking arm previously described. In this structure, resistance arm 6 is substantially inflexible, thereby providing a consistent feel for the operator. However, the actuating surface of resistance arm 6 is so located that it is contacted by the engagement portion of the mating connector (not shown) at the same time as locking arms 5. This creates a very large pressure and makes it difficult for the operator to fit the devices together completely. Moreover, since resistance arm 6 is located between locking arms 5, the latter are displaced outward to provide the necessary space therefor. Thus, the engagement portion of the complementary connector must also be offset outward, thus requiring a different shape thereof.